The present invention relates to artillery projectiles for firing from indirect fire artillery pieces such as artillery guns, mortars and rocket artillery. In particular, it concerns an artillery projectile with separately controlled booster actuation and fragment dispersion arrangements, as well as systems and methods operating such projectiles.
Traditional warheads for artillery projectiles consist essentially of a metal envelope of a thickness sufficient to withstand launch acceleration, filled with a high-explosive charge. As this type of classical warhead has a very limited radius of effectiveness, cargo projectiles have been developed, containing a multitude of small bomblets, each bomblet including an envelope and explosive filler. The cargo warhead is opened as the projectile approaches the target area and the bomblets are dispersed over a large area. The bomblets are detonated upon ground impact and the area is covered by fragmentation generated from the individual bomblets.
While the fragmentation area of the cargo warhead is considerably larger than the one of the unitary projectile warhead, it has a major draw-back: unexploded bomblets pose a serious hazard of death or injury to friendly forces or to civilians that may later enter the coverage area, even a long time after cessation of the hostilities. Although such hazard may be mitigated by providing the individual bomblets with self-destruct mechanisms, such mechanisms have a certain degree of un-reliability and therefore the hazard to friendly forces and civilians is only mitigated but not totally negated.
As an alternative to explosive bomblets, it is possible to employ a cargo warhead carrying inert fragments which cause target damage by kinetic impact alone. In order to be effective, such warheads must generate a hail of high velocity fragments with a sufficient energy to penetrate the intended target. A booster motor is typically provided for this purpose. An example of such a system may be found in U.S. Pat. No. 4,922,826 to Busch et al. (although the Busch et al. document also discusses adding secondary incendiary compositions to the fragments).
Actuation of the booster motor generally also initiates, directly or indirectly, a dispersion mechanism which spreads the fragments over a large area perpendicular to the direction of flight, thereby generating wide area coverage of the target region. In the case of the aforementioned Busch et al. document, a booster motor accelerates and spins each warhead, and an ejection charge is detonated at the end of burning of the booster motor to expel the fragments from the warhead. Timing of the booster and the dispersion mechanism are interdependent, occurring in a fixed time sequence.
A critical factor in operation of inert-fragment cargo warheads is the timing and mechanism of dispersion. If fragments are dispersed too widely, typically due to early triggering of dispersion, the warhead will fail to provide saturation coverage of the targeted area. If on the other hand insufficient dispersion is achieved, typically due to late triggering of dispersion, only part of the targeted area will be hit. Thus, in planning a trajectory of the warhead, the required timing for triggering dispersion typically determines, working backwards, the time and position at which the booster must be actuated. This in turn dictates the trajectory which must be used to bring the warhead to the correct position and attitude for actuating the booster.
It would be advantageous to provide an artillery projectile with separately controlled booster actuation and fragment dispersion arrangements, as well as systems and methods operating such projectiles.